Traveling wave tube



Oct. 14, 1958 MASAMICHI KENMOKU TRAVELING WAVE TUBE Filed March 8, 1956 FIG. I.

FIG. 2. FIG. 3.

v //I 4 C FIG. 4.

INVENTOR ATTO RN EY United States Patent TRAVELING WAVE TUBE Application March 8, 1956, Serial No. 570,315 Claims priority, application Japan May 18, 1955 4 Claims. (Cl. BIS-3.5)

In discharge tubes, such as traveling wave tubes, etc., used for ultra short wave amplification, oscillation, generation, frequency doubling and so forth, there is provided an electron beam directed along a fixed axis for interaction with a wave propagated along a retardation circuit on this axis. In such tubes there is further provided input and output couplers which have element coupler devices fastened to opposite ends of the retardation line, which is usually a helix. The input and output wave guides have flange portions extending along these coupler units to provide a high frequency choke action. At the output end of the tube beyond the end of the choke section is generally provided a target electrode which is insulated from the line both for direct and high frequency currents.

In this conventional configuration the envelope is quite long and thus presents certain difiiculties in handling. Leakage of high frequency energy may also occur at the gap between the coupler unit and the collector.

According to this invention, the traveling wave envelope may be shortened by providing a capacitive coupling between the terminal coupler element and the target electrode so that the target electrode can then serve the function of providing the internal element of the choke used with the output wave guide. This con struction not only permits shortening of the tube but also avoids the danger of high frequency leakage at the output and of the tube.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a diagrammatic sectional view of a traveling wave tube incorporating a feature of this invention.

Figs. 2 and 3 are modified forms of delay line termination and target electrodes for use in the tube of Fig. 1, and

Fig. 4 is a further modification of a terminal electrode structure incorporating the features of this invention.

Turning first to Fig. 1, there is shown, in sectional View, a traveling wave tube having an electron gun I for transmitting a beam internally of a helical delay line 2. The tube envelope 3 has sealed to one end the target or collector electrode 4 which may be exposed directly to the air. At 5 is provided the input coupler unit which serves with the flange on the input wave guide as a choke. This unit 5 is connected directly to the helix 3 by means of a unit 6 and at its other end the helix 2 is connected to a unit 7 fastened directly to a metal disc plate 8. Plate 8 is insulated by an insulating layer 9, which may be of mica or the like, from the collector electrode 4. The output wave guide 10 has a flange 15 overlying the target electrode 4. The inner surface of the target electrode 4, as shown at 4, may be made flush with the inner wall of wave guide 10 and the flange 15 connected directly thereto avoiding the necessity of a choke electrode at the output end. As there is no gap between the walls of wave guide 10' and collector 4 there will be no high frequency leakage past this point, except for the energy which may leak through the insulator 9.

The avoidance of leakage at insulator 9 may be achieved by the structural arrangements indicated in Figs. 2 and 3. In Fig. 2 the coupler unit 7 at the terminal end of the helix 2 is coupled with the collector electrode 4 by means of insulating material 10. Furthermore, an opening penetrating into electrode 4 is provided as shown at electrode 11 so as to receive the electron beam internally thereof. A grid electrode may be arranged across this opening as indicated at 11 so as to picK up any secondary electrons which may be emitted by impingement of the beam on the target electrode.

Fig. 3 is similar in general structure to Fig. 2. However, in this case the hole 12 is provided in target electrode 4 and a pin 13 is used connected to the disc plate 8 and extending out to provide a terminal. 14 for the application of high voltage energy to the helical electrode.

In Fig. 4 is shown a modified form of the invention in which the output coupler electrode 18 is formed as a hollow cylindrical element fastened to the helical delay line by conductor 16. The target electrode 17 is cupshaped and has flange wall portions extending concentrically of the element 18 and insulated therefrom by means of an insulating annulus 19. This element is contained within the envelope 3, and flange 15 of output wave guide 10 is capacitively coupled therewith to provide the output choke. In this case the target electrode 17 is made substantially a quarter wave length long at the mid operating frequency to provide the desired choking effect.

While the invention has been described in connection with a helical delay line, it is clear that the principles of this invention may be applied to other types of travelling tubes using retardation wave guides or concentric lines.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. In a traveling wave tube having a retardation line, a beam source for projecting a beam along said line for interaction with high frequency energy transmitted along said line, input and output couplers for energy in said line and a target electrode for the electron energy of said beam after passage along said line, said output coupler arrangement comprising a coupling means connected to one end of said line providing a capacitive coupling with said target electrode, an output wave guide havingone wall thereof substantially aligned with the end of said target electrode adjacent to said one end, and a choke flange on said wave guide extending coaxially over and coupled to said target electrode.

2. In a tube according to claim 1, the combination wherein said capacitive coupling means comprises a metal disc plate, and insulating material intermediate said disc and said target electrode.

3. In a tube according to claim 2, said combination further comprising a block target electrode, having an Patented Oct. 14, 1958 u L'11: opening part way therethrough aligned with the axis of References Cited in the file of this patent said beam.

4. In a tube according to claim 1, the combination UNITED STATES PATENTS wherein said capacitive coupling means, comprises a cylin- 2,673,900 Mumford M31. 30, 1954 drical terminal for said line, and a target electrode having 5 ,9 Wamecke et a1 111116 1954 an annular portion insulated from and surrounding said 2,752,523 Goodall June 26, 1956 terminal. 

